Development of Solid Oxide Fuel Cell (SOFC)

Solid oxide fuel cell (SOFC) is the ultimate power-generating device that is expected to yield the highest efficiency of power generation among any power generators that use fossil fuels. As a high-quality exhaust heat can be recovered, SOFC is also expected to be a new energy supply system that will contribute to realize a low carbon society. We are working on SOFC development, and pushing for wider adoption of energy systems that can enhance energy security and contribute to a reduction in CO2 emissions.

Objective

SOFC has superior characteristics (outlined below), and are currently being used in the residential co-generation system named ENE-FARM. To promote wider adoption, the durability and reliability of the technology needs to be enhanced while maintaining a low cost. In addition, SOFC systems could open up new markets in business and industry sectors such as office buildings and convenience stores, where the introduction of co-generation has thus far proven difficult due to low heat demands. We are working to develop SOFC systems that can overcome such challenges going forward, and aim for wider adoption of distributed energy supply systems that contribute to a low-carbon society.

SOFC Characteristics

It is possible to generate electricity at high efficiency (over 45% LHV).

The operating temperature is very high (600 to 1,000 ℃) and it is possible to use exhaust heat easily.

Both electricity and heat can be used effectively, as they are generated at a location where they are required.

Various fuels, such as hydrogen, methane and other hydrocarbons, can be used.

The stream-reforming can be conducted at the cell, so it is expected that the cost will be reduced by downsizing and simplifying the reformer to extract hydrogen from town gas.

Approach to widespread residential SOFC

In order to achieve widespread use of residential SOFC, we are researching and developing cell stacks which offer high reliability and durability at a low cost, as well as cost reduction of hot module to incorporate these stacks that can be operated continuously at a high temperature to generate electricity. In particular, we are identifying issues and confirmation of reliability of cell stacks through various evaluations that are intended to be actual operation, such as durability, heat-cycle, start-and-stop, and emergency shutdown tests, and investigating the hot module prototype designs which will enable costs to consumers to be reduced. We are also trying to develop the basic technologies for SOFC, such as assessment of the fundamental properties of SOFC component materials and investigation of advanced methods of degradation analysis to enable early identification of degradation factors.

〔SOFC evaluation system〕 〔Prototype of SOFC hot box〕

Development for higher-efficiency SOFC

We are working toward higher-efficiency SOFC systems to realize a commercial-grade distributed power system that surpasses the generation efficiency of large-scale thermal power stations. We aim to enhance the generation efficiency by increasing the ratio of fuel that can contribute to power generation reactions of SOFC systems. More specifically, by removing CO2 and water vapor generated with the power generation reaction from the exhaust gas of the SOFC fuel electrode, the unreacted fuel can be concentrated and reused, thereby achieving higher efficiency. At Tokyo Gas we are working to develop elemental technologies to support fuel regeneration technology, and heat management technologies to effectively leverage the exhaust heat (reduced compared with conventional systems) inside the equipment. In addition, we are designing and manufacturing systems, and conducting demonstration tests of high-efficiency power generation.

〔Internal structure of prototype equipment used to demonstrate high efficiency〕

Prospects

We will promote distributed energy supply systems that can contribute to the realization of a low-carbon society by working on improving the efficiency, cost, durability and reliability of SOFC.